Once bitten...  

This is the third quest in the D.I.R.T.Y. Excavation Live Event quest line. Once you've completed the quest A Strange Illness Jimbo will ask you to assist him again. He will send you to the Excavation Site and check behind a tent and look for the monkey that bit and infected one of the excavators. Take the carpet right next to Jimbo back to the Excavation Site.

Go behind the tent to the north of the carpet that Researcher Aillena stands in front of and an infected monkey will spawn and attack you. Kill it and return to Jimbo for your reward and the next quest, The Source of Infection.